Structural configurations known as space frames or spatial structures, wherein a plurality of elongated struts are interconnected via a system of nodes or hubs, are well known in the art. One successful hub for such structures is disclosed in U.S. Pat. No. 4,449,843 wherein two hub components are precompressed together by a suitable bolt to form a structural unit capable of transferring axial and shear loads from the struts attached to the hub components. Although this prior art system has generally proved adequate for the purposes intended, it is not perfect and there are problems in manufacture and use thereof. For example, when the bolt used in this prior art system is formed of aluminum, it is difficult or impossible to precompress the aluminum hub components to sufficient values to accommodate significant diagonal loads or to ensure against relative rotation of the hub components.
Accordingly, constructing the bolt of high strength steel is required in order to effect adequate precompression between the hub components to maintain configurative stability of the hub. This difference in materials creates a potential problem of material compatibility and galvanic corrosion between the parts. To avoid this potential problem great care and expense has been expended to have the high strength steel bolts cadmium plated to minimize galvanic action. In addition, the size of the center bolt must be varied to meet various load requirements for efficiency.
There is thus a definite need in the art for an improved hub for connecting multiple strut members in a spatial structure. The present invention is an improvement over the prior art and is intended to include all the advantageous features while minimizing the disadvantages thereof.